An unmarked police car stolen from Redland Bay on Tuesday has been found, but not the gun that was "locked away" inside it.
Wynnum District Inspector Gerry Costello said the second car involved, a black Ford Mondeo had also been found.
"The second car was found in Grafton after the driver crashed it on Wednesday. There were several children in the back of the car," he said.
"We are currently questioning the male driver and a female passenger.
"The gun is still missing."
He said police were urgently appealing for public assistance to help find the black Glock model 27 semi-automatic pistol.
On Wednesday afternoon, the silver Subaru Impreza was found abandoned at Moore Street, Loganlea after a witness reported to police.
Anyone with information about the firearm or the stolen cars can contact Policelink on 131 444 or Crime Stoppers on 1800 333 000.
On Monday the Newman Government announced it was cracking down on the use of illegal firearms.
The move came after two people were shot at the Robina Town Centre last Saturday, and three weeks after a man was shot dead at the Warrigal Square shopping centre in Eight Mile Plains on April 12. Another man was shot dead the same day at his South Rochedale home.